Re: delete-file to trash

[Stefan Monnier <monnier@iro.umontreal.ca>]

>> Regarding trapping, Time Machine uses standard unix hard links, and
>> the default FS format for Mac OS is HFS+, the specs for which are
>> published here
>> (http://developer.apple.com/mac/library/technotes/tn/tn1150.html);
>> a GNU/linux driver has been developed.

> Actually, it is a bit more complicated than that. As an optimization
> feature, if a directory and all its contents are unchanged since the
> previous backup, that directory in the latest backup becomes a hard
> link to the corresponding directory in the previous backup. This is
> one reason Time Machine can only use HFS volumes for Time Machine.
> Example:

> ; ls -1id */mach/System
> [...]
> 14828147 2010-05-19-062015/mach/System/
> 14828147 2010-05-20-083504/mach/System/
> 15557200 2010-05-21-184651/mach/System/
> 15557200 2010-05-22-075716/mach/System/
> 15808642 2010-05-22-131850/mach/System/
> 15808642 2010-05-22-144139/mach/System/
> 15808642 2010-05-22-154126/mach/System/
> 15808642 2010-05-22-164134/mach/System/
> [...]

Interesting.  So it can't be implemented above just any POSIX filesystem
(where hardlinks are only guaranteed to work for files but not for
directories).


        Stefan